The long-term goal of this proposal is to understand the molecular mechanisms of Rib nucleoprotein (RNP) granules. RNP granules are found in a diversity of cells and are typically involved in RNA metabolism. In germ cells of many metazoans, specialized RNP granules, known as germ granules, are required for cell differentiation into functional gametes. The Caenorhabditis elegans germ granule, the P-granule, is required for germline maintenance. P-granule assembly requires the Caenorhabditis sp. specific scaffold proteins, PGL-1 and PGL-3, and the highly conserved Vasa-related DEAD-box helicases, GLH-1 and GLH-4. Vasa helicases are found in all metazoans and are necessary for fertility in mammals. This proposal uses the P-granule as a model to study the assembly and function of germ granules. I will study the mechanistic roles of the PGL and GLH proteins in RNA processing and granule formation, and investigate the molecular function of P-granules. Along the way, I will learn new methods in RNA sequencing, C. elegans genome editing, and single molecule microscopy, enabling me to analyze and test my structural models in vitro and in vivo. The R00 phase will continue using these methods to probe the biological function of P-granules related to assembly dynamics and RNA metabolism. The basic mechanisms of P-granules will undoubtedly provide insight into the function of germ granules in tissue development and a greater overall understanding how RNP granules function in cell biology.